What chemical or biochemical agents do plants use to inhibit each other's growth?

Question

As I just learned, allelopathy is the action by which plants regulate the growth of other nearby plants.

I have hear of ethylene is a general signal for growth and fruit ripening in particular, but I would like to hear about more specific compounds or proteins that are known to be allelopathic agents and how specific can they be - lots of plants ignore each other and just grow over each other.

@AlanBoyd has pointed me to a journal, but as its not open content, I'm hoping for a next level review of the mechanisms and actors in this topic...

thanks in advance!

Answer 1

A classic example is juglone from Black Walnut tree roots. This review from 1973 discusses juglone and allelopathy, inhibiting growth of other trees. This 1961 paper describes juglone's effects as able to sedate or at depress movement of Daphnia magna, leopard frogs, perch, catfish, goldfish, mice, rats and rabbits. That led to work testing juglone on cancer cells.

Answer 2

As with the massive variety of compounds that serve to protect plants against insect and animals, resulting in a wide range of poisons, antibiotics and other natural insecticides, allelopathic compounds are highly varied with different methods of action: some merely prevent germination while others are effectively herbicides.

One example is Alliolaria petiolata. In that species the allelopathic substance is not known, but is thought to ahve a fungicidal effect that impedes mycorrhizal development, which would seriously affect the development of many species.